The Soviet Union (Russia after the czars) agreed to stand by while Germany conquered all of Western Europe. When Germany turned on the Soviets/Russia, it ran into the same problems Napoleon did. As Germany ran out of gas, material and men, Russia filled the power vacuum and occupied Europe (including most of Germany) from the Balkans to the Baltic. It looks to me as if Germany and most of Europe have gotten so eco-friendly they've lost the ability to defend themselves, and Russia's historic thirst for empire is continuing to drive its behavior. France and Germany were so committed to renewable energy they've greened themselves into the weakest possible strategic position. Germany became virtually totally dependent or Russia for gas in the past year when we weakened our petroleum extraction, transport and refinement capacities. Russia annexed portions of Crimea in 2014, giving Russia a warm water port - we did, essentilly nothing. So, in this round, they annex portions of/most of/all of Ukraine (sound like Hitler and Czechoslovakia? mebbe?) without significant resistance. It isn't illogical to think that Poland might be next.
I don't know what the US can do. We handed Putin the leverage we had when we throttled back our petroleum production. Stategically, I don't see how we think that we can engage the Russians in Eastern Europe when we don't have control of the seas, or the air, and would be facing an enemy with significantly more sophisticated armaments than the Taliban/Isis/Arab Brotherhood. We cerainly don't have a political establishment that has given any glimmer that we can project a cogent will to defend Ukraine - or a desire to do so.
I just appears that our foreign policy is to stand around telling the Russians - "Stop it, you big bully. Shame on you!" Our next step will probably to register a complaint - obviously. in the strongest possible terms to - the UN General Assembly.
(Nice one with the Peter the Great shot, Mike.)